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EC number: 905-588-0
CAS number: -
The key chronic study was conducted by NTP (1986). The study comprises the oral gavage administration of mixed xylenes to rats (0, 250, or 500 mg/kg/day) and mice (0, 500 or 1000 mg/kg/day) for 5 days/week for 103 weeks. There was no evidence of carcinogenicity.No studies are available regarding cancer in animals exposed via inhalation to mixed xylene or the individual xylene isomers.
The carcinogenicity of mixed xylene was
investigated in male and female F344/N rats following oral (gavage)
administration at doses of 0, 250 or 500 mg/kg bw/day for 103 weeks.
Animals were observed for survival, clinical signs and body weight gain
and subject to a full necropsy with tissue histopathology at sacrifice.
There was no evidence of treatment-related carcinogenicity in either sex
under these conditions.
No classification of mixed xylenes streams
for carcinogenicity is warranted under DPD or GHS/CLP.
The multi-constituent substances covered by
this registration comprise individual xylene isomers (m-xylene,
o-xylene, p-xylene) and ethyl benzene (>10% - <20%). The following
information is available to characterise their carcinogenic mutagenic
No animal studies are available on the
carcinogenic effects of mixed xylene or the individual xylene isomers
following dermal or inhalation exposure.
The carcinogenicity of mixed xylene (17%
ethyl benzene) following oral exposure has been evaluated in chronic
studies with rats and mice; however, no animal studies are available on
the carcinogenic effects of the individual xylene isomers following oral
exposure. Results of the chronic oral studies with mixed xylene have
been negative (NTP, 1986), with no increase in tumour incidence compared
with the control animals. Treatment involved administration of 0, 250,
or 500 mg/kg/day doses of mixed xylene in corn oil by gavage 5 days/week
for 103 weeks to groups of F344/N rats, 50 animals per group. B6C3F1
mice were treated in a similar manner but given 0, 500 or 1000 mg/kg/day
of mixed xylenes in corn oil by gavage. A large number of gavage-related
deaths were a confounding factor. This study did not comprehensively
examine systemic effects but it did include a complete histopathological
examination of all tissues as well as determination of body weight gain.
Based on histopathology of all organ systems, a NOAEL of 500 mg/kg/day
was observed for rats and a NOAEL of 1000 mg/kg/day was observed for
mice. In conclusion there was no evidence of carcinogenicity of mixed
xylenes following oral administration.
Equivocal results reported by Maltoni et al
(1983, 1985) following exposure of rats to xylenes are viewed to be
unreliable (IPCS, 1997) as analysis was conducted by combining all
tumours; this is an unacceptable basis for analysis particularly in aged
animals. In addition, no data were provided to allow an analysis on an
individual tumour-type basis.
The carcinogenicity of ethyl benzene
following inhalation exposure has been evaluated in chronic studies with
F344 rats and B6C3F1 mice (NTP, 1999). Increases in tumor rates in male
(kidney and testis) and in female rats (kidney), in male mice (lung) and
in female mice (liver) were reported following exposure to 750 ppm (3255
mg/m3) ethyl benzene. The RAR (2008) concluded that genotoxicity was not
the responsible mode in the initiation of the reported tumors and that
other non-genotoxic mechanisms may be involved. Furthermore, the
rapporteur concluded that there is sufficient evidence to conclude that
the kidney tumors in the male and female rats are associated with the
rat strain-specific high incidence of chronic progressive nephropathy
(CPN) which is not found in humans. The testis, liver and lung tumours
were types that occur at high or very high spontaneous rates in the F344
rat and B6C3F1 mice strains used. The rapporteur concluded that
ethylbenzene may enhance tumour development in genetically disposed
animals or reduce the latency periods in tumour development. There are
currently no detailed mechanisms explaining the increase in tumour rates
some species and strain specificity is postulated (RAR, 2008).
Consequently the toxicological significance and relevance to human
health of these findings is uncertain and it is considered that
ethylbenzene does not pose a carcinogenic risk for humans.
There is no data indicating any convincing
evidence of an increased risk of cancer as a consequence of exposure to
xylenes. IARC (1999) has placed xylene in Group 3: "The agent is not
classifiable as to its carcinogenicity to humans". The animal data
indicates that xylenes would not be carcinogenic or genotoxic in humans.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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